Steering and propulsion of marine vessels

ABSTRACT

A ship&#39;&#39;s propulsion and steering assembly is provided in which a propeller works within a propulsion nozzle of the type having recirculation of flow outside the nozzle from exit to entry at low or zero speeds of advance. Steering is provided by four shutter rudders mounted at the nozzle entry and three at the exit. In the straight ahead condition of steering, the outboard pair of the rudder blades at the entry have their leading edges toed out at an angle in the range 3* to 7* while the inboard pair are toed out at an angle of 1* to 3*. The outboard pair of rudder blades at the nozzle exit have their trailing edges toed out at an angle of 1* to 3*.

United States Patent l 1'3,630,164

[72] Inventor Ewan Christian Brew Corlett [5 6] References Cited [21 1 A l N gg gg England UNITED STATES PATENTS pp 0. [22] Filed Jan. 20 1970 3,009,435 11/1961 Horton 114/163 451 Patented Dec. 28, 1971 FOREIGN PATENTS [73] Assignee Hydroconic Limited 1,106,851 7/1955 France 1 14/163 Basingstoke, England Prim E y xammer-Andrew H. Farrell [32] Pnomy i AttorneyDowell & Dowell [33] Great Britain 10,296/69 ABSTRACT: A ship's propulsion and steering assembly is provided in which a propeller works within a propulsion nozzle of the type having recirculation of flow outside the nozzle from exit to entry at low or zero speeds of advance. Steering is provided by four shutter rudders mounted at the nozzle entry and three at the exit. In the straight ahead condition of steering, the outboard pair of the rudder blades at the entry have their [54] STEERING AND PROPULSION OF MARINE VESSELS 4 Claims, 1 Drawing Fig.

[52] US. Cl 114/163 leading edges toed out at an angle in the range 3 to 7 while [51] Int. Cl B63h 25/06 the inboard pair are toed out at an angle of 1 to 3.The out- [50] Field of Search 1 14/163, board pair of rudder blades at the nozzle exit have their trail- 167 ing edges toed out at an angle of 1 to 3".

PATENTEU UEE28 [97! am @JZWW B E I I W Allornez STEERING AND PROPULSION OF MARINE VESSELS This invention relates to the steering and propulsion of marine vessels.

The use of propulsion'nozzles on vessels which have heavily loaded propellers in increasing. Where speeds of advance are very low, as for example in tugs working ships in confined quarters, such nozzles are particularly advantageous.

Where multiple or shutter rudders are use either forward or aft of the propeller disc in the nozzle, or both forward and aft as in our Pat. applications No. 43297/64 and 27l0/66, it has been found that it is necessary to optimize the angles of the rudders which anyway should not be in the fore-and-aft line.

Taking as an example the condition where the speed of ad vance is zero, circulation exists round the nozzle, the flow passing forward along the outside of the nozzle and aft through the inside of the nozzle. This flow is truly fore and aft only along the axis of the nozzle, but at each point laterally displaced at any radius off this central axis the flow is inclined to the fore and aft axis at the entry and the exit to the nozzle, that is to say in the transverse planes of the nose and tail of the nozzle. This inclination of flow to the fore-and-aft axis at all radii other than zero increases as the radius increases, becoming a maximum when very close to the nozzle wall itself. The

inclination increases forward of the plane of the nose and decreases aft of this plane, the inclination becoming zero and the flow axial where the nozzle inner lining is truly cylindrical in way of the propeller disc.

Aft of the propeller disc, if the nozzle is of the decelerating type the flow is angled outwards; but in any case in the transverse plane of the tail of the nozzle, and during circulation conditions of zero advance speed, the flow is angled heavily outwards in order to return forward along the outside of the nozzle.

If under these conditions shutter rudders spaced away from the centerline of the nozzle area are fitted forward of the propeller disc with their mean chord lines fore and aft, they will be at some angle of incidence to the flow into the nozzle entry. Thus they will give rise to an increase in drag, on the one hand, and a loss of circulation round the nozzle, and hence of nozzle thrust, on the other.

According to the invention, in order to remove both these adverse effects such forward shutter rudders are toed with their leading edges outboard of their stocks.

The outer rudders of the shutter system should be toed outward at the leading edges more than rudders further inboard, and in general they will follow closely in the lines of flow of circulation round the nozzle in the horizontal plane through the center of the nozzle.

In the case of trailing rudders aft of the propeller and away from the centerline of the nozzle, the same consideration applies. The flow diverges out and round the tail of the nozzle in order to go forward along the outside. According to the invention the mean chord line of the rudders is angled out with the trailing edge of the rudder outboard of the stock. Where more than one trailing rudder is fitted to one side of the centerline, it is necessary that the outboard rudders be toed out at their trailing edges more than rudders which are inboard of those rudders.

It is an important aspect of the invention that the toeing angles required, in order to give the optimization of nozzle thrust and minimization of profile or induced drag of the rudders, vary with the fore-and-aft position of the rudders. For exampie, if rudders are moved forward at the entry by a constant distance from the entry of the nozzle, then the toeing angle outwards at the leading edge must increase. Similarly with trailing rudders, or rudders aft of the propeller disc, if these are moved out from the exit of the nozzle further aft their toeing angles outward at the trailing edges must increase.

Toeing angles therefore depend upon the position of the rudders. Typical figures for four shutter rudders forward of the propeller are 3 to 7 toeing angle for the outboard rudders and l to 3 toeing angle for the inboard rudders. Typical figures for the after rudders where three shutter rudders are fitted, are 1 to 3 outward for the wing rudders; the centerline rudder does not need to be toed.

One arrangement In accordance with the invention is lllUS- trated by way of example in the accompanying drawing, which is a diagrammatic plan view of a ship's propulsion nozzle hav ing multiple shutter rudders at entry and exit.

The nozzle 11 in the drawing is of the type in which recirculation takes place in the forward direction around the outside of the nozzle especially when the speed of advance is zero. There are four hydrofoilform shutter rudder blades l2, 13 at the entry to the nozzle 11, turning about stock axes l4; and three blades l5, 16 at the nozzle exit turning about axes 17. The general water flow lines at the entry and exit are indicated at 18 and 19, respectively. Within the nozzle there is a propeller, the central plane of the propeller disc being indicated at 20.

As shown, the two outboard blades 12 of the forward shutter rudders are toed out forward each at an angle in the range 3 to 7, while the inboard blades 13 are toed out at an angle in the range I to 3. In the case of the aft shutter rudders, the two outboard blades 15 are set out at their trailing edges each at an angle in the range 1 to 3; but the central blade 16, being on the center line of the nozzle, has no inclination. These angular inclinations of the blades are, of course, those that obtain when the steering is set straight ahead.

What I claim is:

l. A ships propulsion and steering assembly, comprising a fixed propulsion nozzle, a propeller working therein, and multiple shutter rudders at the nozzle entry, said multiple shutter rudders being at least four in number arranged as an inboard pair disposed symmetrically one on either side of the nozzle axis and an outboard pair likewise disposed symmetrically one on either side of the nozzle axis at a lateral distance from said axis greater than the inboard pair, all the rudders being toed out at their leading edges in the straight ahead setting of the steering, and the outboard pair being toed out at a greater angle than the inboard pair in substantial accordance with the nozzle entry flow lines.

2. An assembly according to claim 1, wherein multiple shutter rudders are provided also at the nozzle exit, including at least one pair of rudders disposed symmetrically one on either side of the nozzle axis and toed out at their trailing edges in substantial accordance with the nozzle exit flow lines.

3. An assembly according to claim I, wherein the outboard pair of rudders at the nozzle entry having a toeing angle of 3 to 7 and the inboard pair having a toeing angle of 1 to 3.

4. An assembly according to claim 2, wherein said pair of rudders at the nozzle exit having a toeing angle of l to 3, there being also a central rudder at the nozzle exit having no toeing angle. 

1. A ship''s propulsion and steering assembly, comprising a fixed propulsion nozzle, a propeller working therein, and multiple shutter rudders at the nozzle entry, said multiple shutter rudders being at least four in number arranged as an inboard pair disposed symmetrically one on either side of the nozzle axis and an outboard pair likewise disposed symmetrically one on either side of the nozzle axis at a lateral distance from said axis greater than the inboard pair, all the rudders being toed out at their leading edges in the straight ahead setting of the steering, and the outboard pair being toed out at a greater angle than the inboard pair in substantial accordance with the nozzle entry flow lines.
 2. An assembly according to claim 1, wherein multiple shutter rudders are provided also at the nozzle exit, including at least one pair of rudders disposed symmetrically one on either side of the nozzle axis and toed out at their trailing edges in substantial accordance with the nozzle exit flow lines.
 3. An assembly according to claim 1, wherein the outboard pair of rUdders at the nozzle entry having a toeing angle of 3* to 7* and the inboard pair having a toeing angle of 1* to 3*.
 4. An assembly according to claim 2, wherein said pair of rudders at the nozzle exit having a toeing angle of 1* to 3*, therebeing also a central rudder at the nozzle exit having no toeing angle. 